Wireless power transmission method, and wireless power transmission device

Abstract

To provide a wireless power transmission capable of coexisting with wireless communication while improving power supply efficiency.SOLUTION: In a wireless power transmission method for transmitting electric power by sending radio waves in space, when a channel-clear state continues for a duration of at least 500 milliseconds after detecting a channel-clear state in which no other radio waves on the same channel as the radio wave are being transmitted in the space, the radio waves are sent into the space after waiting a period of at most 50 milliseconds.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a wireless power transmission method and a wireless power transmission device. [Background technology]

[0002] As described in Non-Patent Document 1, a space transmission type wireless power transmission system that transmits power using radio waves is under study. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Information and Communications Council, Information and Communications Technology Subcommittee, Land Wireless Communications Committee ~Working Group on Space-Based Wireless Power Transmission Systems~ Report (Draft) Summary, [online], May 2020, [Retrieved January 13, 2023], Internet<URL:https: / / www.soumu.go.jp / main_content / 000694293.pdf> [Non-Patent Document 2] ARIB STD-T107 "Specific low-power radio station 920MHz band mobile identification radio equipment" [Patent documents]

[0004] [Patent Document 1] JP 2006-60310 A Summary of the Invention [Problem to be solved by the invention]

[0005] Wireless power transmission, which transmits power using radio waves, is required to coexist with existing systems such as wireless communication for sending and receiving data and RFID (Radio Frequency IDentification), and to improve power supply efficiency, but previous studies have been insufficient.

[0006] An object of the present disclosure is to provide a technology for achieving coexistence with wireless communication and improving power supply efficiency with respect to wireless power transmission. [Means for solving the problem]

[0007] A wireless power transmission method according to one embodiment of the present disclosure is a wireless power transmission method that transmits power by transmitting radio waves into space, and when a channel clear state in which no other radio waves on the same channel as the radio waves are being transmitted in the space is detected and the channel clear state continues for a period of at least 500 milliseconds, the method waits for a period of at most 50 milliseconds and then transmits the radio waves into the space.

[0008] A wireless power transmission device according to one embodiment of the present disclosure is a wireless power transmission device that transmits power by transmitting radio waves into space, and includes a monitoring unit that monitors whether other radio waves on the same channel as the radio waves are being transmitted in the space, a control unit that waits for a maximum of 50 milliseconds and then decides to transmit the radio waves if the channel clear state continues for a period of at least 500 milliseconds after detecting a channel clear state in which the other radio waves are not being transmitted, and a transmitting unit that transmits the radio waves from a specified antenna based on the decision of the control unit.

[0009] Furthermore, these comprehensive or specific aspects may be realized by a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. Effect of the Invention

[0010] According to the present disclosure, it is possible to realize wireless power transmission that can coexist with wireless communication and that can improve power supply efficiency. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing an example of a wireless power supply system according to an embodiment of the present invention. [Diagram 2] Diagram for explaining conventional carrier sense [Diagram 3] FIG. 1 is a block diagram showing a configuration example of a wireless power transmitting device according to an embodiment of the present invention. [Figure 4] FIG. 1 is a diagram for explaining state transitions related to a wireless power transmission method according to an embodiment of the present invention; [Diagram 5] 1 is a flowchart showing an example of a wireless power transmission method according to the present embodiment. [Figure 6] FIG. 1 is a diagram showing a first example of the operation of a conventional wireless power supply system that performs carrier sensing. [Figure 7] FIG. 1 is a diagram showing a first example of an operation of a wireless power supply system that performs a wireless power transmission method according to an embodiment of the present invention. [Figure 8] FIG. 13 is a diagram showing a second example of the operation of a conventional wireless power supply system that performs carrier sensing. [Figure 9] FIG. 11 is a diagram showing a second example of the operation of the wireless power supply system that performs the wireless power transmission method of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters and duplicated description of substantially the same configuration may be omitted. This is to avoid the following description becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0013] (Present embodiment) <Wireless power supply system> FIG. 1 is a block diagram showing an example of a wireless power supply system 1 according to the present embodiment.

[0014] The wireless power feeding system 1 is a system that transmits power using radio waves, and includes at least one wireless power transmitting device 10 and at least one wireless power receiving device 20, as shown in FIG.

[0015] The wireless power transmitting device 10 transmits radio waves for transmitting power to the wireless power receiving device 20. The wireless power receiving device 20 obtains power by receiving the radio waves transmitted from the wireless power transmitting device 10. Hereinafter, the transmission of radio waves for transmitting power by the wireless power transmitting device 10 may be referred to as wireless power transmission, and the reception of the radio waves transmitted from the wireless power receiving device 20 by the wireless power transmitting device 10 may be referred to as wireless power reception.

[0016] The wireless power transmitting device 10 may be a device having only a wireless power transmitting function, or may be a device having a communication function such as an RFID interrogator. The wireless power receiving device 20 may be a sensor terminal, a display terminal, an actuator, a charger, a power receiver, a light, a speaker, or an integrated version of these.

[0017] The radio waves for power transmission may be microwaves. The frequency band (carrier) of the radio waves for power transmission may be 920 MHz, 2.4 GHz, or 5.7 GHz. The wireless power transmitting device 10 and the wireless power receiving device 20 may be set to use a common frequency band.

[0018] When wireless power supply is performed using microwaves, it is possible to avoid interference by performing carrier sense in order to reduce the influence on a wireless communication system existing near the wireless power supply system 1. Fig. 2 is a diagram for explaining conventional carrier sense. In Fig. 2, the horizontal axis t indicates elapsed time.

[0019] As shown in FIG. 2, a conventional wireless power supply method waits for a predetermined period of time, then performs carrier sense (CS) for a predetermined period of time to check whether other radio waves are being transmitted on the channel used for wireless power transmission, and starts wireless power transmission if it is confirmed by the carrier sense that no other radio waves are being transmitted (see Non-Patent Document 2).

[0020] However, in the conventional wireless power supply method, when multiple wireless power transmission devices are present in the vicinity, while one wireless power transmission device is performing wireless power transmission, the other wireless power transmission devices continue carrier sense, and therefore wireless power transmission cannot be performed. That is, unlike wireless communication for transmitting or receiving data, wireless power supply systems for transmitting energy do not have the disadvantage of interference between multiple waves. However, in the conventional wireless power supply method, while one wireless power transmission device is performing wireless power transmission, the other wireless power transmission devices do not perform wireless power transmission, which leads to a decrease in power supply efficiency in the entire wireless power supply system.

[0021] In addition, since wireless power transmission transmits energy, it tends to use a channel for a long time compared to wireless communication. Therefore, when multiple wireless power transmission devices exist, after one wireless power transmission device finishes wireless power transmission, the other wireless power transmission devices will perform wireless power transmission without delay, and the ratio of the period during which the wireless communication system can use the channel becomes extremely small. In order to avoid this, it is possible to make the carrier sense period of the wireless power transmission device longer than the carrier sense period of the wireless communication system, but in that case, the probability that the wireless power transmission device can use the channel becomes low, leading to a decrease in power supply efficiency.

[0022] In the conventional technology shown in Patent Document 1, multiple RFID readers are synchronized using a synchronization signal other than the frequency that the system itself is going to use. However, this technology cannot operate in cooperation with unknown wireless communication systems that use the same frequency band, and they will interfere with each other. Furthermore, since the system itself needs a frequency for the synchronization signal in addition to the frequency that it uses for wireless communication, there is a problem that the occupied frequency bandwidth increases.

[0023] Therefore, in this embodiment, a technique for improving power supply efficiency using a single frequency while also taking into consideration the impact on a wireless communication system will be described.

[0024] <Configuration of wireless power transmission device> FIG. 3 is a block diagram showing an example of a configuration of a wireless power transmitting device 10 according to the present embodiment.

[0025] As shown in FIG. 3, the wireless power transmitting device 10 includes a control unit 11, a monitoring unit 12, a transmitting unit 13, and an antenna 14.

[0026] The control unit 11 performs processing for realizing the functions of the wireless power transmitting device 10. Details of the processing will be described later (see FIG. 5). The control unit 11 may be configured with a processor, a controller, a central processing unit (CPU), a large scale integration (LSI), a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or the like. The control unit 11 may also include a memory capable of storing data. The wireless power transmitting device 10 may also be configured with a software defined radio (SDR), or the like, in which case the control unit 11 may be implemented by software.

[0027] The monitoring unit 12 monitors the state of the channel through which wireless power transmission is to be performed. For example, the monitoring unit 12 monitors whether or not other radio waves are being transmitted through the channel, and generates channel state information indicating the monitoring result. The monitored channels may include the channel through which wireless power transmission is to be performed, as well as other channels on which wireless power transmission causes interference. The monitoring unit 12 may provide the generated channel state information to the control unit 11. The other radio waves may be wireless power transmission transmitted by another wireless power transmitting device 10, wireless communication transmitted by a wireless communication system, or other radio waves.

[0028] Examples of wireless systems using the 920MHz carrier band include digital MCA relay stations and mobile stations, advanced MCA mobile stations, mobile phone (LTE) base stations and mobile stations, RFID, radio astronomy, etc. Examples of RFID include indoor wireless (passive tag 1W), specific low power (passive tag 250mW), telemeter, telecontrol and data transmission wireless equipment (active tag), etc.

[0029] Examples of wireless systems that use the 2.4 GHz band carrier include wireless LAN systems, mobile identification (indoor radio stations or specific low-power radio stations), unmanned mobile high-speed transmission systems (robot radio systems), mobile satellite radio systems (N-STAR), mobile satellite radio systems (Globalstar), broadcasting carrier radio stations (FPUs), radio astronomy, amateur radio, etc.

[0030] Examples of wireless systems that use 5.7 GHz carriers include wireless LAN systems, DSRC (narrow range communications) systems, STL / TTL systems for broadcasting operations, FPU / TSL systems for broadcasting operations, unmanned mobile high-speed transmission systems (robot radio systems), weather radar, radio astronomy, and amateur radio.

[0031] The transmitter 13 transmits power wirelessly from the antenna 14 based on a decision or instruction from the controller 11 .

[0032] The antenna 14 transmits radio waves related to wireless power transmission into space. Although there is one antenna 14 in Fig. 3, there may be a plurality of antennas 14. In addition, when there are a plurality of antennas 14, the transmitting unit 13 may use the plurality of antennas 14 to perform wireless power transmission by beamforming or the like.

[0033] In addition, the wireless power transmitting device 10 shown in FIG. 2 is configured to perform wireless power transmission and carrier status monitoring using a single antenna 14, but the wireless power transmitting device 10 may be configured to have a separate antenna 14 for wireless power transmission and an antenna for channel status monitoring.

[0034] Furthermore, at least a part of the functions of the monitoring unit 12 and / or the transmission unit 13 may be included in the control unit 11, and at least a part of the functions of the monitoring unit 12 may be included in the transmission unit 13.

[0035] <Wireless power transmission method> FIG. 4 is a diagram for explaining the state transition related to the wireless power transmission method according to the present embodiment. In FIG. 4, the horizontal axis t represents the passage of time. FIG. 5 is a flowchart showing an example of the wireless power transmission method according to the present embodiment. Next, with reference to FIGS. 4 and 5, the processing related to the wireless power transmission method performed by the wireless power transmission device 10 will be described.

[0036] The control unit 11 initializes the monitoring timer Tm (Tm = 0) (S101). The value of the monitoring timer Tm increases with the passage of time.

[0037] The control unit 11 acquires channel state information from the monitoring unit 12 and determines whether the channel for performing wireless power transmission is cleared (S102). That the channel is cleared means that no other radio waves are being transmitted in the channel, and that the channel is not cleared means that other radio waves are being transmitted in the channel.

[0038] If it is determined that the channel is not cleared (S102: NO), the control unit 11 returns the process to step S101. That is, until the channel is cleared, the monitoring timer Tm is not started and the value of the monitoring timer Tm does not increase.

[0039] If it is determined that the channel is cleared (S102: YES), the control unit 11 determines whether the monitoring timer Tm is greater than or equal to the channel clear period Tcs (Tm ≧ Tcs) (S103).

[0040] If the monitoring timer Tm is less than the channel clear period Tcs (Tm < Tcs) (S103: NO), the control unit 11 returns the process to step S102.

[0041] If the monitoring timer Tm is equal to or longer than the channel clear period Tcs (Tm≧Tcs) (S103: YES), the control unit 11 proceeds to the process of the next step S104. That is, the control unit 11 does not proceed to the process of the next step S104 until the channel clear state continues for the channel clear period Tcs or longer. Also, if the control unit 11 detects the transmission of another radio wave on the channel before the channel clear state continues for the channel clear period Tcs or longer (that is, if step S102 is NO), the process returns to step S101 and initializes the monitoring timer Tm.

[0042] In step S104, the control unit 11 waits for a waiting period Twt without starting wireless power transmission (S104). During this waiting period Twt, the control unit 11 does not need to acquire channel state information from the monitoring unit 12. That is, during this waiting period Twt, the control unit 11 does not need to determine whether the channel is cleared or not.

[0043] After waiting for a waiting period Twt, the control unit 11 instructs the transmission unit 13 to perform wireless power transmission for a wireless power transmission period Ttx (S105). The transmission unit 13 receives the instruction and performs wireless power transmission from the antenna 14 for the wireless power transmission period Ttx. Then, the process returns to step S101. While performing wireless power transmission, the control unit 11 does not need to acquire channel state information from the monitoring unit 12.

[0044] <Example of operation> Next, an example of operation when each wireless power transmitting device 10 performs the above-mentioned process shown in FIG. 5 will be described.

[0045] 6 and 7 are diagrams for explaining an operation example of a wireless power supply system in which 10 wireless power transmission devices are arranged at a low density. Fig. 6 shows an operation example of a wireless power supply system that performs a conventional carrier sense. Fig. 7 shows an operation example of a wireless power supply system 1 that performs the wireless power transmission method of the present embodiment. The low density may be, for example, a density of about 10 wireless power transmission devices distributed in an area of ​​10,000 square meters.

[0046] 6 and 7, the upper graphs 101 and 103 show the period during which each wireless power transmitting device is transmitting power wirelessly, the numbers on the vertical axis show the identification numbers of the wireless power transmitting devices, and the horizontal axis shows the elapsed time (ms). Each graph line of the upper graphs 101 and 103 shows whether the wireless power transmitting device with the identification number is transmitting power wirelessly or not, the period when the graph line is above shows the period during which wireless power transmission is performed, and the period when the graph line is below shows the period during which wireless power transmission is not performed.

[0047] 6 and 7, the lower graphs 102 and 104 show the number of wireless power transmitting devices performing wireless power transmission at each elapsed time, with the vertical axis showing the number of wireless power transmitting devices performing wireless power transmission and the horizontal axis showing the elapsed time (ms).

[0048] In a conventional wireless power feeding system that performs carrier sense, as shown in the upper graph 101 of Fig. 6, wireless power transmitting devices that are relatively far away can transmit wireless power simultaneously, but wireless power transmitting devices that are relatively close can only transmit wireless power to one another due to carrier sense. Therefore, as shown in the lower graph 102 of Fig. 6, two to four wireless power transmitting devices always transmit wireless power, and there is no free time on the channel. Therefore, there is no room for the wireless communication system to perform wireless communication.

[0049] In contrast, in the wireless power feeding system 1 performing the wireless power transmission method of the present embodiment, each wireless power transmitting device 10 performs the process shown in Fig. 5, so that the timing of (channel clear period Tcs+waiting period Twt) of each wireless power transmitting device 10 is synchronized and the timing of wireless power transmission is also synchronized, as shown in the upper graph 103 of Fig. 7. Therefore, as shown in the upper graph 103 and the lower graph 104 of Fig. 7, during the synchronized (channel clear time Tcs+waiting period Twt), an empty period occurs in the channel. Note that (channel clear period Tcs+waiting period Twt) may also be referred to as a non-power transmission period. Therefore, the wireless communication system can perform wireless communication by utilizing this empty period of the channel.

[0050] 7, ten wireless power transmitting devices 10 simultaneously perform wireless power transmission during the wireless power transmission period Ttx. Therefore, power supply efficiency is improved compared to a conventional wireless power supply system that performs carrier sense.

[0051] 8 and 9 are diagrams for explaining an example of operation of a wireless power supply system 1 in which 10 wireless power transmission devices are arranged at high density. Fig. 8 shows an example of operation of a wireless power supply system that performs conventional carrier sensing. Fig. 9 shows an example of operation of a wireless power supply system 1 that performs the wireless power transmission method of the present embodiment. The high density may be, for example, a density of about 10 wireless power transmission devices distributed in an area of ​​100 square meters.

[0052] The upper graphs 105, 107 and the lower graphs 106, 108 shown in Figures 8 and 9 should be interpreted in the same way as the upper graphs 101, 103 and the lower graphs 102, 104 shown in Figures 6 and 7. Therefore, the explanation of the graphs will be omitted here.

[0053] In a conventional wireless power feeding system that performs carrier sense, as shown in the upper graph 105 of Fig. 8, a specific wireless power transmitting device performs wireless power transmission, and other wireless power transmitting devices stop performing wireless power transmission due to carrier sense. Therefore, as shown in the lower graph 106 of Fig. 8, about one wireless power transmitting device always performs wireless power transmission, and there is no idle time in the carrier. Therefore, there is no room for the wireless communication system to perform wireless communication.

[0054] In contrast, in the wireless power feeding system 1 performing the wireless power transmission method of the present embodiment, each wireless power transmitting device 10 performs the process shown in Fig. 5, so that the (channel clear period Tcs+waiting period Twt) (i.e., non-power transmission period) of each wireless power transmitting device 10 is synchronized, and the timing of wireless power transmission is also synchronized, as shown in the upper graph 107 of Fig. 9. Therefore, as shown in the upper graph 107 and the lower graph 108 of Fig. 9, an empty time occurs in the channel during the synchronized waiting period Twt. Therefore, the wireless communication system can perform wireless communication by utilizing this empty time of the channel.

[0055] 9, ten wireless power transmitting devices 10 simultaneously perform wireless power transmission during the wireless power transmission period Ttx. Therefore, power supply efficiency is improved compared to a conventional wireless power supply system that performs carrier sense.

[0056] Also, as shown in the upper graph 101 of Fig. 6, wireless power transmitting devices that are relatively far apart from each other may not recognize each other's presence and may transmit wireless power simultaneously because their received power values ​​are below the carrier sense threshold. This may cause radio interference, similar to the hidden terminal problem in CSMA / CA. On the other hand, in the upper graph 103 of Fig. 7, although there are wireless power transmitting devices 10 that cannot directly recognize each other, they can operate autonomously in synchronization by repeating relays.

[0057] 7 and 9, the timing of wireless power transmission is synchronized in a shorter time in the wireless power feeding system 1 in which the wireless power transmitting devices 10 are arranged at a high density, compared with the wireless power feeding system 1 in which the wireless power transmitting devices 10 are arranged at a low density, thereby further improving the power feeding efficiency.

[0058] <Why wireless power transmission timing is synchronized> As shown in Fig. 4 and Fig. 5, when a period during which no other radio waves are transmitted continues for a channel clear period Tcs, each wireless power transmitting device 10 waits for a waiting period Twt and starts wireless power transmission. The reason for providing the waiting period Twt is to absorb the variation in accuracy of the monitoring timer of each wireless power transmitting device 10 and to ensure synchronous operation when two or more wireless power transmitting devices 10 exist. A specific example will be described below.

[0059] If the waiting period Twt is not provided, wireless power transmission starts immediately after the channel clear period Tcs continues. In this case, if there is a variation in accuracy such that the monitoring timer of the first wireless power transmitting device counts a little faster than the monitoring timer of the second wireless power transmitting device, the first wireless power transmitting device starts wireless power transmission a little earlier, and the second wireless power transmitting device detects the wireless power transmission sent by the first wireless power transmitting device during channel clear monitoring and cannot start wireless power transmission. Therefore, in this embodiment, the occurrence of such a problem is avoided by providing the waiting period Twt. As a result, as shown in the graphs of FIG. 7 or FIG. 9, the transmission start timings of the wireless power transmitting devices 10 are automatically synchronized, and the waiting period Twt absorbs the variation in accuracy of the monitoring timers of the wireless power transmitting devices 10, and as a result, the wireless power transmission periods Ttx of the wireless power transmitting devices 10 can be synchronized.

[0060] The channel clear period Tcs may be a predetermined period. The channel clear period Tcs may be, for example, 500 ms or more. The channel clear period Tcs may be read as a first period. The standby period Twt may be a predetermined period. The standby period Twt may be, for example, greater than 0 ms and less than or equal to 50 ms. The standby period Twt may be read as a second period. The wireless power transmission period Ttx may be a predetermined period. The wireless power transmission period Ttx may be, for example, greater than or equal to 2000 ms and less than or equal to 2500 ms. The wireless power transmission period Ttx may be read as a third period. The above-mentioned predetermined channel clear period Tcs, standby period Twt, and wireless power transmission period Ttx may be set in each wireless power transmitting device 10. As a result, a common channel clear period Tcs, standby period Twt, and wireless power transmission period Ttx are set for the multiple wireless power transmission devices 10, so that the standby periods Twt and wireless power transmission periods Ttx of the multiple wireless power transmission devices 10 are synchronized, as shown in FIG. 7 or FIG. 9.

[0061] The channel clearing period Tcs may be longer than the waiting period Twt, which improves the probability of detecting the presence of other wireless communications.

[0062] The wireless power transmission period Ttx may be longer than the channel clear period Tcs or the standby period Twt, thereby ensuring a sufficient wireless power transmission period Ttx and improving power supply efficiency.

[0063] The wireless power receiving device 20 can obtain larger power by receiving wireless power from a plurality of wireless power transmitting devices 10 than by receiving wireless power from a single wireless power transmitting device 10. In the wireless power feeding system 1 according to the present embodiment, as shown in Fig. 7 or 9, the plurality of wireless power transmitting devices 10 can perform wireless power transmission in a common period, so that the wireless power receiving device 20 can obtain larger power. This improves the power feeding efficiency.

[0064] <Application examples of wireless power supply systems> The wireless power supply system 1 according to the present embodiment may be configured to operate by reducing the wireless power transmission output of the wireless power transmitting device 10 so as to conform to a specified low-power radio station when using the 920 MHz band. This makes it unnecessary to apply for and register a license for wireless use, and allows the wireless power supply system 1 to be used in a wider variety of situations. In this embodiment, by monitoring the channel, the wireless power supply system 1 can be operated without affecting a wireless communication system that should be used preferentially, such as an in-house radio station. In addition, even if the wireless power transmission output of each wireless power transmitting device 10 is reduced so as to conform to a specified low-power radio station, the wireless power supply system 1 according to the present embodiment can realize a system in which the wireless power receiving device 20 can obtain sufficient power, since the multiple wireless power transmitting devices 10 can transmit wireless power in synchronization with each other, as shown in FIG. 7 or FIG. 8.

[0065] For example, the license-free wireless power supply system 1 according to the present embodiment may be applied to a logistics truck. In this case, the wireless power supply system 1 may supply power to a sensor terminal or the like attached to a package carried by the truck, to accessories in the truck's cabin, and to a sensor terminal or the like installed in a tire of the truck.

[0066] Summary of the Disclosure The above description of the embodiments discloses the following techniques.

[0067] <Technology 1> The wireless power transmission method of the present disclosure for transmitting power by transmitting radio waves into space transmits the radio waves into the space when a state in which no other radio waves are being transmitted in the space continues for at least a first period (e.g., a channel clear period Tcs), after waiting for a second period (e.g., a waiting period Twt). As a result, as exemplified in FIG. 7 or FIG. 9, the second period and the timing of transmitting the radio wave are synchronized, so that coexistence with wireless communication for transmitting or receiving data and improvement in power supply efficiency can be achieved.

[0068] <Technology 2> In the wireless power transmission method according to Technique 1, the radio waves may be transmitted for a third period (for example, a wireless power transmission period Ttx). As a result, as exemplified in FIG. 7 or FIG. 9, radio waves are sent out synchronously in the third period, improving power supply efficiency.

[0069] <Technology 3> In the wireless power transmission method according to Technique 2, the first period, the second period, and the third period may be predetermined periods. As a result, the first period, the second period, and the third period are set in common to the multiple wireless power transmitting devices 10, and the second period and the third period can be synchronized as illustrated in FIG. 7 or FIG. 9.

[0070] <Technology 4> In the wireless power transmitting method according to any one of Techniques 1 to 3, the first period may be longer than the second period. This makes it possible to appropriately set a balance between the first period and the second period.

[0071] <Technology 5> In the wireless power transmission method according to Technology 4, the third period may be longer than the first period or the second period. This ensures a sufficient third period for transmitting radio waves for power transmission, improving power supply efficiency.

[0072] <Technology 6> In the wireless power transmission method according to any one of Techniques 1 to 5, the radio wave and the other radio wave may be in a common frequency band. This makes it possible to prevent interference between radio waves for power transmission and other radio waves in a common frequency band.

[0073] <Technology 7> In the wireless power transmission method described in Technique 6, the frequency band may be a 920 MHz band, a 2.4 GHz band, or a 5.7 GHz band. This makes it possible to prevent interference between radio waves for power transmission and other radio waves in the common 920 MHz band, 2.4 GHz band, or 5.7 GHz band.

[0074] <Technology 8> The wireless power transmission device 10 according to the present disclosure, which transmits power by transmitting radio waves into space, includes a monitoring unit 12 that monitors whether other radio waves are being transmitted in the space, a control unit 11 that decides to transmit the radio waves after waiting for a second period (e.g., a waiting period Twt) if the state in which the other radio waves are not being transmitted continues for at least a first period (e.g., a channel clear period Tcs), and a transmitting unit 13 that transmits the radio waves from a specified antenna 14 based on the decision of the control unit. As a result, as exemplified in FIG. 7 or FIG. 9, the second period and the timing of transmitting the radio wave are synchronized, so that coexistence with wireless communication for transmitting or receiving data and improvement in power supply efficiency can be achieved.

[0075] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, corrections, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also belong to the technical scope of the present disclosure. In addition, the components in the above-mentioned embodiments may be arbitrarily combined within the scope of the invention. [Industrial Applicability]

[0076] The technology disclosed herein is useful for technology for transmitting power using radio waves. [Explanation of symbols]

[0077] 1. Wireless power supply system 10 Wireless power transmission device 11 Control section 12 Monitoring Department 13 Transmitter 14 Antenna 20 Wireless power receiving device 101, 103, 105, 107 Top graph 102, 104, 106, 108 Lower graph

Claims

1. A wireless power transmission method for transmitting power by transmitting radio waves into space, comprising: when a channel clear state in which no other radio waves of the same channel as the radio waves are being transmitted in the space is detected and the channel clear state continues for a period of at least 500 milliseconds, waiting for a period of at most 50 milliseconds, and then transmitting the radio waves into the space; Wireless power transmission method.

2. The period for transmitting the radio wave is a predetermined period. The wireless power transmission method according to claim 1 .

3. The radio wave and the other radio wave are in a common frequency band, The frequency band is 920 MHz, 2.4 GHz, or 5.7 GHz. The wireless power transmission method according to claim 1 or 2.

4. A wireless power transmission device that transmits power by transmitting radio waves into space, a monitoring unit that monitors whether or not another radio wave of the same channel as the radio wave is being transmitted in the space; a control unit that, when a channel clear state in which no other radio waves are being transmitted is detected and the channel clear state continues for a period of at least 500 milliseconds, waits for a period of at most 50 milliseconds and then decides to transmit the radio waves; A transmitting unit that transmits the radio wave from a predetermined antenna based on the determination of the control unit. Wireless power transmission device.

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